1. Technical Field
The present invention relates to a liquid droplet ejection head and a liquid droplet ejection apparatus, and more particularly, to a liquid droplet ejection head and a liquid droplet ejection apparatus provided with such a liquid droplet ejection head.
2. Related Art
In a liquid droplet ejection apparatus such as an ink jet printer, a liquid droplet ejection head is provided for ejecting liquid droplets. It is known to public that such a liquid droplet ejection head is provided with ink chambers (cavities) which store an ink therein and are communicated with nozzles for ejecting the ink in the form of the liquid droplets, and piezoelectric elements which deform wall surfaces defining the ink chambers.
When such a liquid droplet ejection head is driven, a part of the ink chambers (a vibration plate) is deformed by expanding and contracting the piezoelectric elements. By doing so, volumes of the ink chambers are changed, so that the liquid droplets of the ink are ejected from the nozzles.
In the meantime, such a liquid droplet ejection head is produced by bonding a nozzle plate in which the nozzles are formed and a substrate in which through-holes that serve as the ink chambers are formed using an adhesive agent.
However, when the adhesive agent is supplied between the nozzle plate and the substrate, it is difficult to strictly control a supply amount of the adhesive agent. Therefore, it is impossible to uniform the supply amount of the adhesive agent, which results in forming an uneven distance between the nozzle plate and the substrate. In the thus produced liquid droplet ejection head, a volume of each ink chamber becomes ununiform.
Further, a distance between the nozzle plate of the liquid droplet ejection head and a print medium such as a print sheet becomes uneven. Furthermore, there is a possibility that the adhesive agent is run out from a bonded portion (between the nozzle plate and the substrate). These problems cause decrease of dimensional accuracy of the liquid droplet ejection head and quality of prints printed by the ink jet printer.
Additionally, the adhesive agent is exposed to an ink stored in the ink chambers for a long period of time. In this case, the adhesive agent is alterated or deteriorated by organic components contained in the ink. For these reasons, there are possibilities that a liquid-tight property of the ink chambers is lowered and components contained in the adhesive agent are dissolved in the ink.
On the other hand, it is known that respective parts constituting a liquid droplet ejection head can be bonded by a solid bonding method. The solid bonding method is a method in which these parts are directly bonded to each other without use of an adhesive layer constituted of an adhesive agent. Examples of such a solid bonding method include a diffusion bonding method, a silicon direct bonding method, an anodic bonding method and the like (see JP-A-2007-62082).
However, the solid bonding method has the following problems: (A) constituent materials to be bonded are limited to specific kinds, (B) a heat treatment using a high temperature (e.g., about 700 to 800° C.) must be carried out in a bonding process, (C) an ambient atmosphere in the bonding process is limited to a reduced atmosphere, (D) it is difficult to obtain a state that the parts of the liquid droplet ejection head are partially bonded together, and the like.